Use %zd to output size variables; %td for pointer differences

[khwilliamson]

Throughout the code when trying to output these things, various means have been used to try to get them to work without warnings on architectures with differing word sizes.

But for several releases, we have the 'z' length modifier that is appropriate for any siZe variables. So %zd and %zu can be used with any STRLEN, Size_t, or SSize_t variable, without having to do casts and using things like IVdf, which make the format harder to read.

Similarly there is the 't' length modifier for pTrdiff_t type expressions. Subtracting any two pointers creates an expression of this type according to the C standard. Again casts etc, can be eliminated and there should be no fear of exceeding limits.